The pin tumbler cylinder lock has been used since the mid-19th century to restrict unauthorized access to an item, an enclosure, or a location, for example, as a door lock. A conventional pin tumbler cylinder lock 10, as shown in FIG. 1A, includes a cylinder plug 20 rotatable in a cylinder housing or shell 30. The plug 20 and shell 30 each include a series of channels 25, 35, with the plug channels 25 intersecting a keyway 27 in the plug 20. When the lock 10 is in a locked condition, pin sets including outer driver pins 39 and inner tumbler pins 29 extend radially through the aligned plug and shell channels 25, 35, with springs 38 disposed in the shell channels 35 to bias the driver pins 39 partially (and typically at varying distances for each pin) into the cylinder channels 25 to prevent rotation of the plug 20 with respect to the shell 30. When an authorized key is inserted into the keyway of the lock (not shown), notches on the key engage the tumbler pins 29 and slide the tumbler pins 29 and driver pins 39 against the springs 38, such that each tumbler pin 29 is substantially disposed in the corresponding plug channel 25, and each driver pin 39 is substantially disposed in the corresponding shell channel 35, clearing a shear line between the plug 20 and the shell 30. When this shear line is clear, the driver pins 35 and tumbler pins 25 are each in a position of non-interference with respect to the intersections of the plug and shell channels 25, 35, and the cylinder plug 20 is permitted to rotate within the shell 30 and unlock an associated locking member, such as a dead bolt (not shown).
The conventional pin tumbler cylinder lock may be susceptible to unauthorized opening. As one example, lock picking involves the use of thin picks inserted in the keyway to manipulate the driver and tumbler pins to position the pins for rotation of the plug. As another example, as illustrated in FIGS. 1A and 1B, a technique referred to as “bumping” involves the insertion of an impact transmitting device, such as, for example, a “bump” key K into the keyway 27 of a pin tumbler cylinder lock 10 such that bitted portions B on the key K align with each of the channels 25. By bumping or rapping the inserted bump key K, the impact forces of the bitted portions striking the tumbler pins 29, as shown by arrows in FIG. 1B, is translated to the driver pins 39, causing the driver pins 39 to momentarily separate from the tumbler pins 29 along the intersections of the plug and shell channels 25, 35, and move fully within the shell channels 35, thereby allowing rotation of the bump key K and plug 20 as the bump key K is rapped. This separation of the driver pin 39 from the tumbler pin 29 may occur upon impact of the tumbler pin with the driver pin (a “pool ball” type effect), or after bumping, where the tumbler pin begins to drop back into the plug channel 25 before the driver pin 39 begins to drop. As known in the art, other impact transmitting devices, such as, for example, a vibratory pick gun or blowgun, operate under the same principle, by impacting the tumbler pins 29, which in turn impact and move the corresponding driver pins 39.